I plan to start this week or next. I have ordered about 10 models from Shapeways, and plan to open my shop to start selling the first design I think is ready for marketing (just got the first test prints last week - more on that later, in another thread).
I think their business model is great - for those who don't know, Shapeways allow anyone to sell things via a shop on the Shapeways site. It works like this: a designer models something, uploads the file to his/her shop, sets the price (cost from Shapeways plus markup), and promotes their product(via social marketing, blogs, etc). Customers come to the shop, place an order, pay Shapeways, Shapeways fulfills the order and pays the designer (the markup amount).
Some pros:
-zero cost to the designer
-designer never has to stock inventory
-Shapeways handles the money processing and any customer service issues
Some cons:
-Customer has to wait 2-4 weeks to receive the order while Shapeways makes it
-Material selection is somewhat limited
-Marketing is up to the designer, if you don't let people know about your product, nobody will buy it (this could also be seen as a pro...)